Thanks to science, we know more and more about what is going on in a wine as it’s taking shape in the cellar or evolving in bottles. But as French researcher Régis Gougeon has been finding out, we’ve only seen the tip of the iceberg.
In the complex biochemical composition of wine, there are about 1,500 to 2,000 known compounds that have been identified. Thanks to new analytical techniques, in particular an approach called metabolomics, he thinks the actual number of components may be much higher. “If we extrapolate a little from what we’ve seen through these techniques, it looks like there might be closer to 60 or even 70,000 components present in wine.”
How did this become apparent? Simply put, metabolomics allows researchers to show a full portrait of every chemical compound present in wines by taking a picture of everything present instead of digging in to analyze single compounds, one or several at a time.
“It’s like a photo of a landscape, with a higher resolution than we ever had before,” he adds. “And as we look a little closer, we see that there are compounds that we know from research outside of wine, and then others that we hadn’t seen appear anywhere before.”
It’s enough to make one’s head spin, a little, but Gougeon remains cool-headed, looking at these new possibilities: “All this doesn’t contradict what we knew up to now, but we can see that there are a lot of subtleties that escape us, once we start looking at these analyses,” he says.
Markers and fingerprints
There are many applications for this approach, which can help detect and characterize many aspects of wine’s composition, origin and even the effects of winemaking techniques. One of the earlier studies performed by Gougeon and a team of researchers, using this technique, helped identify specific origins of oak in wine. Through this “non-targeted, high-resolution” approach, they were able to draw up the specific signature of oak from a specific forest, and then to see it show up within a wine’s composition.
The oak markers are durably inscribed in the wine’s composition, and so are others related to winemaking techniques. Studying some 320 Chardonnays from two different vintages (2006 and 2007) that had received two different levels of SO2 additions at the time of pressing, Gougeon and his colleagues showed that signatures linked to the level of added sulphites remained present in the wines over several years. The “memories” of sulphur treatment were shown to have lasting effects, showing how such a basic treatment can significantly influence a wine’s personality.
Another ground-breaking study looked at the prevalence of terroir effect verses vintage effect in wines from three distinct vineyards over three different vintages. The verdict? When looking at the whole chemical “landscape”, it was possible to see vintage differences show up in similar manners in all three wines, and while the vintage effect was overall more significant, there were differences between the wines that remained consistent from year to year and were therefore attributable to the intrinsic differences between the three different plots – in other words, terroir. “There are constants that modulate every other element in more or less significant ways, and the different vineyards show different characters, consistently, which basically confirms what professional tasters have been saying.”
This consistency in the way the wine presents itself in different terroirs also suggests another possibility for the technique: authenticating a wine’s very specific origin. Could this “fingerprinting” approach actually help make sure that, for instance, grand cru wines could be certified to avoid counterfeiting? “That immediately came to mind for us, since you have access to the whole range of imprints”, says Gougeon.
At this point, these new methods seem to be constantly generating new research possibilities – including going from the general to the particular or, in other words, to look to the specific components that are lighting up the wine’s landscape in the non-targeted approaches. “The next logical step is to identify the components that we see reacting without having identified them,” explains Gougeon. For once, seeing the forest and the trees doesn’t seem contradictory, but rather complementary.
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